Method of filling electric incandescent lamps, discharge tubes or the like with gas and of sealing the same



March 28, 1967 H. PACE 3,311,439

METHOD OF FILLING ELECTRIC INCANDESCENT LAMPS, DISCHARGE TUBES OR THE LIKE WITH GAS AND OF SEALING THE SAME Filed March 22, 1963 INVENTOR.

HENRI PACE W 2. AGENT United States Patent 3 Claims. (in. 316-24) The invention relates to a method of filling an electric incandescent lamp, a discharge tube or the like with a gas and of sealing the same, in which the interior of an open lamp or tube is traversed by a flow of an inert gas at above atmospheric pressure, for example nitrogen gas so that at least the ambient air cannot enter into the lamp or tube, this flow being maintained until the lamp or tube is sealed. Such a method is known and is used, for example, for filling of an electric incandescent lamp or the like with a gas without preliminary pumping. A small excessive pressure can be obtained in the lamp or tube then.

In the known method the desired filling gas, for example iodine vapour, is added to the inert gas, which thus also flows through the lamp or tube. There will in this case be a certain amount of loss of filling gas; therefore this method is less efiicient for filling a lamp with precious filling gases.

The invention has for its object to provide such as improvement of said method that it can be employed for the manufacture of lamps or tubes having filling gas formed mainly by a precious rare gas, for instance xenon or krypton, the loss of this precious gas occurring in the sealing operation being substantially negligible.

The method according to the invention is characterized in that prior to sealing a quantity of a comparatively precious, inert rare gas, e.g. xenon or krypton gas is introduced into the lamp or tube said gas being condensed on a wall portion strongly cooled by e.g. liquid nitrogen in the interior of the lamp or tube, said gas staying in the lamp or tube after sealing. Consequently the functions of rinsing or protecting and filling are separated from each other. For rinsing or protecting a cheap, inert gas e.g. nitrogen gas may be used, whereas a given quantity of a precious, inert rare gas e.g. the readily condensable xenon or krypton can be used for filling; there will be substantially no loss of this gas.

An advantage of the use of xenon or krypton and of a cooling agent e.g. liquid nitrogen consists in that after sealing and after removal of the cooling agent a pressure of several atmospheres can be formed in the lamp or tube at room temperature. It should be noted that it is known per se to obtain a final pressure in a closed container by means of a cooling agent, said pressure exceeding slightly the atmospheric pressure.

The invention also provides a device for carrying out the method according to the invention. This device, which comprises, as is known, a hollow needle to be introduced into the unsealed lamp or tube, through which needle a gas under excessive pressure can be introduced and which needle can be withdrawn when the lamp or tube is sealed, has the feature that the hollow needle has two or more separate longitudinal channels. This hollow needle can be inserted into the lamp or tube via an exhaust tube or another unsealed portion.

The invention will be described more fully with reference to the drawing, in which FIG. 1 shows a first embodiment of a tubular lamp not needle 18.

yet sealed at one end, which must be filled with a precious gas and be sealed without preliminary pumping.

FIGS. 2, 3, 4 and 5, 6, 7 are plan views and side elevations respectively of three preferred hollow needles, each having two separate gas-supply channels and FIG. 8 shows a second embodiment of an electric incandescent lamp provided with an exhaust tube.

In the manufacture of tubular lamps a tube 12, sealed previously at one end, can be held by means of a bracket 13 in the manner shown in FIG. 1 with respect to a head 14. The lower end of the tube 12 has a metal strip 10, which constitutes the connection between a current supply Wire 1a and an incandescent body 17; the strip 10 is completely surrounded by the glass material of the tube 12. The head 14 comprises a resilient member 15, which holds a second current supply wire 16, which is connected via a further metal strip 11 with the incandes cent body 17. In the head 14 is furthermore provided a hollow needle 18, which is vertically movable. In FIG. 1, the flames emanating from one or more burners are indicated by arrows :by means of which flames the upper end of the tube 12 can be sealed off. While the hollow needle 18 is moved upwardly, the upper end may assume the same shape as the lower end of the tube 12.

In a known method first the undesirable atmosphere of the tube 12 is expelled by means of an inert rinsing gas before the tube 12 is sealed with the aid of the flames. In this embodiment nitrogen gas is used. The nitrogen gas supplied through the hollow needle 18 can leave the tube, while it expels the undesirable atmosphere of the tube. The arrangement is such that at least the ambient air cannot penetrate into the tube. Consequently, the lamp is rinsed without pumping. Then a filling gas e.g. an active vapour is added to the rinsing gas. The mixture is introduced into the tube 12 through the hollow In the known method provisions are made that, during the sealing operation, the mixture introduced through the hollow needle 18 continues passing through the tube until the latter is sealed at its upper end and the hollow needle 18 has been moved upwardly. This gives rise to a loss of active vapour. Particularly, if the filling gas is precious, e.g. in the case of xenon or krypton, the loss of said gas renders the known gas-filling method fairly costly.

In accordance with the invention this loss is reduced to a negligible extent. The previous inert rare gas, xenon or krypton is first separated from the supply of the cheaper inert gas e.g. nitrogen gas. For the separate supply of the two gases use may be made of a hollow needle having one of the shapes shown in FIGS. 2, 3, 4 or 5, 6, 7. These needles have two separate longitudinal channels 18a and 18b. Through the channel 18a the cheaper nitrogen gas is supplied, whereas the supply of a given quantity of the precious xenon or krypton is introduced through the channel 18b.

Prior to the sealing operation, while a flow of nitrogen gas is permanently maintained, a given quantity of the comparatively precious xenon or krypton gas is introduced into the tube. Care is taken, that this precious gas cannot leave the tube. To this end said gas is condensed on a strongly cooled wall portion of the tube 12 (20). Use may be made of a container 29 filled with liquid nitrogen, which surrounds the lower end of the tube 12 to a given level.

While the flow of the cheaper nitrogen gas is maintained during the sealing operation at the upper end of the tube 12, the xenon or krypton gas stays in the interior of the tube. After sealing operation the container 19 is removed and at room temperature a pressure of a several atmospheres will be produced inside the mainly xenonor krypton-filled, sealed tube 12.

It should be noted that due to the maintenance of a fiow of nitrogen gas during the sealing operation a protective effect is obtained by this gas flow, so that oxidation of the metal strip 11, which is strongly heated during the sealing operation, is avoided.

The glass envelope 21 of a lamp shown in FIG. 8 has two pinches in which metal strips 22 and 23 connecting an incandescent body 24 and current supply wires 26 and 27 are completely surrounded by glass material. The lamp has furthermore an exhaust tube 28, through which rinsing and filling can be performed and which is sealed in the last stage of the manufacture. Like the lamp described in FIG. 1, this lamp can be filled with xenon or krypton.

What is claimed is:

1. A method of filling an electric lamp with gases and sealing the same comprising introducing an inert gas under pressure exceeding atmospheric pressure into said lamp until said lamp is sealed thereby preventing the penetration of ambient air into said lamp, introducing a quantity of an inert rare gas into said lamp prior to sealing and while the flow of said inert gas in said lamp is maintained, and cooling at least a part of said lamp whereby the inert rare gas is condensed thereon, said inert rare gas remaining inside said lamp during the sealing operation.

Z. A method of filling an electric lamp with gases and sealing the same as claimed in claim 1 wherein said inert gas under pressure is hydrogen and said inert rare gas is selected from the group consisting of xenon and krypton.

3. A method of filling an electric lamp with gases and sealing the same as claimed in claim 1 wherein said part of said lamp is cooled by liquid nitrogen.

References Cited by the Examiner UNITED STATES PATENTS FRANK E. BAILEY, Primary Examiner.

GEORGE N. WESTBY, R. L. JUDD,

Assistant Examiners. 

1. A METHOD OF FILLING AN ELECTRIC LAMP WITH GASES AND SEALING THE SAME COMPRISING INTRODUCING AN INERT GAS UNDER PRESSURE EXCEEDING ATMOSPHERIC PRESSURE INTO SAID LAMP UNTIL SAID LAMP IS SEALED THEREBY PREVENTING THE PENETRATION OF AMBIENT AIR INTO SAID LAMP, INTRODUCING A QUANTITY OF AN INERT RARE GAS INTO SAID LAMP PRIOR TO SEALING AND WHILE THE FLOW OF SAID INERT GAS IN SAID LAMP IS MAINTAINED, AND COOLING AT LEAST A PART OF SAID LAMP WHEREBY THE INERT RARE GAS IS CONDENSED THEREON, SAID INERT RARE GAS REMAINING INSIDE SAID LAMP DURING THE SEALING OPERATION. 